Process of making cyclic monomeric disulfides



United States Patent Ofiice 2,7 15,635 Patented Aug. 16, 1955 PROCESS OF MAKING CYCLIC MONOIVIERIC DISULFIDES Franklin 0. Davis, Trenton, N. J., assignor, by mesne assignments, to Thiokol Chemical Corporation, Trenton, N. J., a corporation of Delaware No Drawing. Original application August 2, 1952, Se-

rial No. 240,067, now Patent No. 2,657,198, dated October 27, 1953. Divided and this application February 6, 1953, Serial No. 335,597

2 Claims. (Cl. 260-327) This invention relates to new cyclic compounds having a disulfide linkage, the polymerization thereof to produce polymers useful as plastic compounds, protective coatings, casting materials and the like and methods of making said ring compounds.

There are numerous references in the literature to heterocyclic sulfur compounds containing one or several monosulfide groups. There are, on the other hand, no thoroughly substantiated cases of simple heterocyclics containing disulfide groups in the rings and no indications of the novel properties of such heterocyclic compounds.

There are many advantages in substances which without the necessity of solvents or dispersion media can be made, stored, and transported in the form of a liquid and which can be converted when desired from the liquid condition into a high polymer having rubbery or other useful characteristics. It is further advantageous when such liquids can be so converted by a process of true polymerization, as distinguished from condensation, because then the polymerization can be efiected without the large change in volume and density which accompanies condensation reactions. Such physical changes are fre quently accompanied by cracks and other flaws in the resultant casting. A liquid having the above-mentioned characteristics is a useful casting compound because it can be poured into a mold, will readily fill the spaces and interstices therein and can then, without large shrinkage, be converted into a solid molded product having rubbery or other useful characteristics.

The outstanding properties of the polysulfide polymers in respect to solvent resistance are well known and their usefulness for many applications is unquestionably valuthe various liquid polysulfide polymers now available. These liquid polymers while advantageous in many respects, still require curatives generally in stoichiometric or larger amounts in order to be converted into a polymer by oxidation of thiol to disulfide groups. The low molecular weight liquids of this invention, on the other hand, are converted to solid rubbery or plastic polymers by use of only small, catalytic quantities, of converting materials. It is thus obvious that these materials possess many advantages not present in the line of liquid polymers, now available, which are capable of conversion to the polysulfide polymers. Previous to the mercaptan liquid polymers the only way of obtaining these polymers was by the reaction of halide and polysulfide resulting in an aqueous latex or suspension, ofiering numerous disadvantages in many instances. The liquid compounds of this invention present advantages over the thiol terminated liquid polymers in that they are much less viscous and are nevertheless capable of converting readily to a high polymer. They are, in fact, the only true monomers of the polysulfide type of polymer.

Genetically the invention comprises new compositions of mater responding to the generic formula their production and polymerization. The general formula of a preferred class of said cyclic disulfides is Z is a member of the group consisting of O, S, OCH2O, SCH2S-, OC2H4O-, SC2H4S, and CH2'.

In accordance with the invention the monomeric ring compounds of the invention are polymerized by treatment with a catalyst. The polymerization of these disulfide rings is quite surprising and would not be expected from the chemical structure of the compounds. The organic aliphatic disulfides, either monomeric or polymeric, are quite stable compounds.

The present invention provides new compounds responding to the above criteria, methods of polymerizing them and methods for producing them.

In accordance with the invention, monomeric ring compounds are produced and polymerized, examples of able. The desirability and usefulness of such polymers such monomeric ring compounds being those having the when obtained from liquids is clearly demonstrated by following structures:

1 CHr-O-GHZ (1A) CH2O-CH1 (1B) CHz-O-CH:

HzS-S H2 S S OH: H2

HzS s CH:

(2) CHz--S CH2 (2A) CHr-S-CH: (2B) CHi-SCH2 H2SS--CH2 s-s (3H, CH1 3112-8 s H;

(a) 01120 CHzO-CH: (3A) 0H20 01320-0111 (33) 0112-0 cmo 0H, Hz-SSCH2 S-S H2 3H: H2SS( )Ha (4) CH2-S ems-CH1 (4A) CHRS 011180112 (413) 01128 CHQS CH1 H;rS-S CH2 ss (3H, H1 dH-S-S JHQ (5) CH2OC2H4OCH: (5A) OHzOCzHrOCHa (5B) CHPOC2H4OCH2 Hn-SSCH: ss (EH1 H: CH2S s--( )H,

(6) CH2S C2H4S 0H: (6A) CHQS 021145 0H1 (6B) CHZS 0111 8 CH, HaS-SCH: S-S (3H7 H2 'diethyl formal.

OHzCHzCHI (8) onh n-ona I s -s. where R is a member of the group consisting of H, CH3 and OH V J H2SS H2 7 where R is a member of the group consisting of hydrogen, alkyl, aryl and aralkyl radicals, examples of such radicals being methyl, ethyl, propyl, n-butyl, n-amyl, benzyl and phenyl.

The following examples illustrate the polymerization of'such ring compounds.

Example 1.Polymerization of Compounds 1, 1A and 1B 100 cc. of the cyclic dithiodiethyl oxide (Compound 1 above), which is an oil at room temperature, are mixed atroom temperature, e. g. 25 C. with 2 cc. of a 25 per cent solution of sodium methylate in methanol and the mixture is poured into-a mold. Polymerization begins immediatelywithout heating and in about 24 hours a rubbery polymer is obtained which becomes tough in about 48 hours. Heat is evolved during the reaction, i. e. the reaction is exothermic.

Example 2.Polymerization of Compounds 1, 1A and 1B Proceed as in Example 1 using 10 cc. of the sodium methylate solution. The polymerization proceeds faster 7 and a tough rubber is obtained within a few minutes.

Example 3.Polymerization of Compounds 2, 2A and 2B in thoroughly to disperse the water in the cyclic formal.

Polymerizationproceeds spontaneously without the necessity of heating and is completed in about 48 hours. The polymer a soft rubbery material.

Example 5 .Polymerization of Compounds 4, 4A and 4B Proceed as in Example 4 substituting the cyclic dithio:

diethyl thioformal (Compound No; 4) for the dithio- This reaction is much slower than that with the corresponding oxygen monomer.

Example,6.Polymerization of any of'the above mentioned cyclic disulfides 100 cc. of any of the above mentionedcyclic disulfides,

e. g. Compound 1 are mixed with 5 cc. of a ten per cent 6 solution of NaSH in absolute ethyl alcohol.

Polymerization begins immediately without heating and in about 2 hours a solid high polymer is obtained.

Example 7 .Polymerization of any of the above 7 mentioned cyclic disulfides Example '8.Polymerization of any of'the above it mentioned cyclic disulfides Proceed as in Example 6 using as catalyst 5 cc. of a 10 per cent solution of NazSz Where x is a number (fractional or whole) greater than 1 and not greater than 6.

Example 9.Polymerization of any of the above mentioned cyclic disulfides Proceed as in Example 6 using as catalyst 5 cc. of a 10 per cent solution of benzyl trimethyl ammonium butoxide in butanol.

Example 10.Polymerization of any of the above mentioned cyclic disulfides Proceed as in Example 6 using as catalyst 2 cc. of diethylene-triamine.

Example 11.P0lymerization of Compounds 1, 1A and 1B To one liter of water containing A. mol of NazS4, 10 cc. of a 5 per cent solution of sodium salt of alkyl naphthalene sulfonic acid and a dispersion of magnesium hydroxide prepared by the interaction of 50 cc. of a 50 per cent MgClz6I-I2O and 50 cc. of a 20 per cent solution of NaOH in water are added. This mixture is heated to F. and there is added slowly l0O-gra-msofCom pound 1. This is heated for 30 minutes at 180 F. then the polysulfide solution is washed out and the latex when free of polysulfide is coagulated by acidfication. It gives a polymer closely resembling a polymer prepared in Example A below but not contaminated with thioxane or the other impurities which may be present from the original reaction.

Example 12.-P0lymerization of a mixture of Compounds 1 and 2 Proceed as in Example 2 using a mixture of 55 cc. of Compound #1 and 50 cc. of Compound #2. In this case a fairly rapid polymerization takes place. The product is a copolymer having rubbery properties which is composed of equimolecular proportions of thioether and ether disulfides.- Latices of these types, if mixed, would not give co-polymers unless given 'a polysulfide treatment. r r 7 A variety of catalysts may be used including alkali alcoholates and alkaline sulfides, hydrosulfides and polysulfides, e. g. the sulfides, hydrosulfides and polysulfides of sodium, potassium, ammonium, calcium, barium, etc. 7

Even water alone acts as a catalyst as illustrated by Examples 4 and 5.

Other classes of materials which can be effectively' used as. catalysts are those of the group consisting of alkyl and aralkyl substituted ammonia compounds and alkyl and aralkyl substituted ammonium compounds. Examples of those compounds are as follows:

i. 'ALKYL AND ARALKYL SUBSTITUTED AMMONIA COMPOUNDS (AMINES) H2NC2H4NHC2H4NH2 Diethylene triamine H2 H-NH: Hr- A! H2 Cyclohexyl amine (HOC2H4) 3N Triethanol amine H2NC2H4NHC2H4NHC2H4NHC2H4NH2 Tetraethylene pentamine CH3(HO2H4)2N Methyl diethanol amine ciinmoczriom Butyl diethanol amine om N on,

N CH2 Hexamethylen'e tetramine H2NC2H4NH2 Ethylene diamine H2NC2H4N HC2H4NHC2H4NH2 liriethylene tet'r'amine 2. ALKYL AND ARALKYL SUBSTITUTED AMMONIUM COMPOUNDS (C2H5)4NOC2H5 Tetraethyl ammonium ethoxide (CILS)4NOC1H9 Tetramethyl ammonium butoxide CeHsCH2(C2H5)3NOC4H9 Benzyl triethyl ammonium butoxide CsHsCHz(C2H5) (CHs'lzNOCd-Is Benzyl dimethyl ethyl ammonium butoxide (CH3)NOC2H5 Tetramethyl ammonium ethoxide (C4H9)4NOC4N9 Tetrabutyl ammonium butoxide CsH5CH2(C4H9)3NOC4 I-I9 Benzyl tributyl ammonium butoxide CsH5CH2(C4H9) (C2H5) (CH3)NOC4H9 Methylethyl butyl benzyl ammonium butoxide HOC2H4NH3OH Monoethanol ammonium hydroxide (HOC2H4)2NH2OH Diethanol ammonium hydroxide (HOC2H4)3NHOH Triethanol ammonium hydroxide H3NC2H NH3 Ethylene bis ammonium hydroxide mNoimNnoinlNm Diethylene amino bis ammonium hydroxide Ammonia can also be used as a catalyst.

The amount of catalyst used may vary from a very small amount, say 005% to a quite large amount, the maximum being dependent on the physical properties desired in the final polymer. Large amounts of catalysts will increase the polymerization rate, but will, of course, remain in the polymer and thus ai fect the properties. The preferred range is 1 to 10% of catalystbased on the amount of cyclic compound used.

Very little is known of the mechanism of this polymerization, but it is, in the final result, the conversion of a cyclic monomer to a linear polymer, according to It is believed that the catalystacts by first adding to and opening the ring by breaking the link between the sulfur atoms. The product which may be momentarily a free radical or an ion can then recombine to give the original starting material, or can react with another similar unit to give a polymer with elimination of the catalyst or its conversion to some type of terminal group. In view of the high polymeric nature of the product, it is thought that the catalyst is eliminated for the most part from the molecule.

Instead of polymerizing a single cyclic disulfide, mixtures of 2 or more of said cyclic disulfides may be polymerized to make copolymers having closely controllable properties.

One general method of making the cyclic disulfides is to first make a polyalkylene polysulfide polymer having polymeric units of the same empirical formula as that of the desired ring compound and then subject the polymer, in the form of an aqueous dispersion, to steam distillation.

For example Compounds 1 to 9 mentioned above may be made as above stated from linear polymers having the following repeating units As is Well known, linear polymers having repeating polyalkylene disulfide units may be made by reacting polyalkylene polyhalides with alkaline polysulfides e. g. the polysulfides of the alkali and alkaline earth metals and ammonium. The alkaline polysulfides include the disulfides, trisulfides, tetrasulfides, pentasulfides and hexasulfides. The resulting linear polymers are composed of repeating units having the general formula and to the sulfur of the above shown disulfide linkage, labile or isosulfur may also be attached. Said linear polymers may also be made by oxidizing polymercaptans, as is also Well known. See for example Patrick Patents 2,216,044, September 24, 1940, and 2,142,145, January 3, 1939.

A theory of the formation of the ring compounds is that during steam distillation of the chain polymers, some of the units thereof break off and form cyclic compounds by union of terminal sulfur atoms of said units. The mechanism of the ring formation is not known but is such that ring formation and elimination appears to regenerate the group so that the reaction acts in a chain mechanism and does not diminish until the polymer is substantially gone, or until a monosulfide or other nonlabile group is encountered in the chain.

The following examples illustrate the above-mentioned method of making the ring compounds i. e. the cyclic disulfides.

Example A.'-Pr0duction of Compound 1 Three mols, for example, 972 cc. of 3.09 molar Na2S4.27 was treated with one gram of the sodium salt of butyl naphthalene sulfonic acid, eight grams of sodium hydroxide and 25 grams of MgCl2.6H2O all used as approximately 25 per cent solutions. This reaction mixture was heated to a temperature of 140 F. and there was added to this reaction mix 2.7 mols (386 grams) of ClC2H4OC2I-I4Cl. The feed period was minutes during which a latex formed in the reaction. This latex was distilled with steam until 1000 cc. of distillate had been collected in order to remove all of the congeneric 1,4-thioxane formed in the reaction. After one washing evidenced by its rate of removal inthe steam distillation,

was quite slow, it.continued practically unchanged for a considerable period of time, for example, about two months of distillation. If other halides are used other polymers are obtained which give different cyclic materials having different physical properties and different degrees of stability. To produce Compound 1A, proceed as above using dichloro methyl ether instead of bis B-"chlorethyl ether. To produce Compound 13 proceed as above using his (gamma chloro propyl) ether.

Example B.Pr0duction of Compound 2 Proceed as in Example A except instead of 386 grams of dichloro-ethyl ether use 429 grams of CIC2H4SC2H4C1 and proceed as before. To produce Compounds 2A and 2B, proceed as above using bis(chloromethyl)thioether and bis( gamma chloro propyl) thioether.

Example C.Production of Compound 3 Proceed as in Example A using instead of dichloroethyl ether 467 grams of his beta .chloroethyl formal ClC2I-I4OCH2OC2H4Cl and proceed as before. To produce Compound 3A proceed as above using bis (chloromethyl) formal instead of bis beta chloroethyl formal. To produce 3B proceed as above using bis(gamma chloropropyl) formal.

Example D.Pr0duct ion of Compound 4 Proceed as in Example C using equirnolecular proportions of his beta chloroethyl thioformal.

C1C2H4SCH2SC2H4C1 pound 4A proceed as above using his (chloromethyDthioformal instead of his 'beta chloroethyl thioformal. To produce 413 proceed as above using his (gamma chloropropyl) thioformal.

Example E.-Production of Compound 5 Proceed as in Example A using instead of dichloroethyl ether 505 grams of triglycol dichloride ClC2H4OC2H4OC2H4Cl and proceed as before. To produce Compound 5A proceed as above using his (chloromethoxy) ethane instead of dichloro ethyl ether. To produce 5B proceed as above using bis (gamma chloropropoxy) ethane.

' Example F.'-Pr0ducti0n of Compound 6 40 instead of the formal of Example C. To produce Com- Proceed as in Example E using equimolecular propor- Example G.-Producti0n of Compound 7 Proceed as in Example A using equimolecular proportions of 1,5 dichloro n-pentane instead of'the dichloroether' of Example A and using the same proportions of NazSezv in the form however of a l-molar solution in osopropanol. Toproduce Compound 7A proceed as above using trimethylene dichloride instead of dichloroether; To produce .7B proceed as above using-heptamethylene dichloride- Proceed as in Example A except that equirnolecular proportions of 1,3 dichlor n-propane instead of the BB dichloroethyl ether of Example 1, are used. That produces Compound 8 where R is hydrogen. To produce other compounds responding to the general formula of Compound 8 (see above) use equimolecular proportions of the substituted 1,3 dichlor n-propanes, i. e. where R is CH3 and OH, respectively.

Example I.-Producti0n of Compound 9 Proceed as in Example A using equimolecular proportions of his (betachloroethyl) amine. That pro duces Compound 9 where R is hydrogen. To produce other compounds responding to the general formula of Compound 9 use equimolecular proportions of N-substituted bis (beta chloroethyl) amines where R is an alkyl, aryl or aralkyl radical.

The yield of ring compound as obtained by distillation of washed polymer latex in some cases is quite small.

This yield may be increased, in any'case, by the addition of a small amount of sodium hydroxide to the latex. The quantity of sodium hydroxide or other strong hydroxides, such as potassium, required for this purpose, may vary from 0 to 25 molar per cent but is advantageously used between 5 and 10%.

All of these polymers prepared as above described, and also the polymers from other halides similarly prepared, have been found to yield these cyclic materials. In many cases extremely small quantities are found, the quantity being so small that it is necessary to extract the cyclic material from the clear distillate. However, all of the cyclic materials possess this capability of repolymerization to the polymer from which they have'been prepared and this polymerization will .take place spontaneously unless all traces of moisture or catalyzing influences are carefully removed. Samples which have been carefully purified in'respect to moisture and catalyzing influences are capable of indefinite storage in glass.

In the above manner, polymeric C2H4S2 yielded on steam distillation a powder in the distillate. This resulted from the cyclic material presumably originally present.

If benzene is added to the distillingflask as the distillation proceeds, the distillate contains dissolved in the benzene an extremely small amount of oil possessing a 7 strong unpleasant odor which very rapidly polymerizes to a powder resembling the original ethylene disulfide polymer. In this case it has proved up to the present time impossible to isolate any of the monomeric 4 membered ditnethylene disulfide ring.

Trimethylene disulfide distills, in the procedure of Example H, at a very fast rate but polymerizes'in the condenser to give'a paper-like cast unless benzene is fed Into the system. If benzene is fed in, as above described,

1 there is obtained a yellow distillate which on drying is stable for a few hours. In this case the 5 membered trimethylene'disulfide ring originally present polymerizes very rapidly to a paper-like polymer i. e. hard and brittle polymer. It could not berobtained free from the benzene.

Z-methyl trimethylene disulfide distills, in the procedure of Example H, over at a very fast rate to give'a yellow oil with slightly better stability than'that of the straight tn'methylene disulfide. The oil may be obtained and has a powerfulunpleasant odor. It polymerizes F quite rapidly 'to give a hard horn-like material.

Z-hydroxy trimethylene disulfide distills, in 1 the procedure of Example H, yielding the ring-material at a fairly good rate as a pale yellow oil which can be isolated. Samples so far obtained have not been very stable but presumably could be stabilized if necessary by extreme desiccation. This oil polymerizes quite rapidly but in this case gives most unexpectedly a crystalline structure in the resulting polymer in spite of the fact that said polymer thus obtained is a soft wax-like maa terial.

(C2H4SC2H4S2) obtained as in Example B distills easily giving a fairly good yield of a pale colored oil which when dried apparently has complete stability. It polymerizes fairly slowly if a trace of moisture is present or quite rapidly with suitable catalysts. On polymerization it gives a tough horn-like material.

(C2H4OC2H4S2) obtained as in Example A above distills with steam yielding an oil at a fairly good rate. This oil is pale yellow in color and, as stated before, has complete stability if dry and free of catalysts. On polymerization it yields a rubber similar to the starting polymer from which it was prepared.

(CZH4OC2H4S4) behaves in almost all respects the same as the corresponding disulfide polymer yielding apparently the same oil, but at a slower rate.

(C2H4OCH2OC2H4S2) on steam distillation gives a distillate which is colorless and perfectly clear. From this solution by ether extraction there is obtainable a very pale yellow oil which it dry has good stability and which may be polymerized with water or other catalysts to a rubber. This ability to polymerize in the presence of water is very nicely demonstrated by this material since if the distillate is allowed to stand over-night it becomes milky and the polymer will settle out as a skin or powder in the bottom of the flask.

(C2H4OC2H4OC2H4S2) likewise distills to give a clear solution in the distillate. On standing it likewise will deposit a small amount of polymer. If, however, the solution is extracted with ether shortly after distillation there is obtained then an extremely small amount of an oil with a slight color. This oil apparently crystallizes at a temperature only slightly below room temperature and its condition as an oil or solid is dependent on the temperature.

The above represents a number of examples of materials of this type obtained by this method. All of the polysulfide polymers so far distilled have given varying amounts of similar compounds in the distillate, the yield in some cases being only a few hundredths of a per cent.

It has been found that the rate of formation of the monomeric disulfides is faster when dry distillation is used instead of steam distillation. An example of dry distillation is as follows:

Example K A poly thio polymercaptan prepared in accordance with U. S. Patent 2,466,963, issued April 12, 1949 to Patrick et al., and having a molecular weight of about 2000 to 25,000 is mixed with 5 to 75 per cent by weight of a caustic alkali e. g. KOH or NaOH. The mixture is heated at pressure of about 0.1 mm. to 20.0 mm. and temperatures of 50 C. to 500 C. until the distillation of the monomeric disulfide slows to an appreciable rate. In an illustrative example i. e. where the polymeric unit is SCzH4OC2H4S the yield of corresponding monomeric disulfide was 51 per cent by weight in about two hours of distillation as compared with about one month to obtain the same yield by steam distillation.

Polysulfide polymers in general can be thus treated i. e. polysulfide polymers comprising recurring units selected from the group consisting of SRS- and R (S): where S is a sulfur atom, R is a radical having a sulfur-connected valence of two and R is a radical having a sulfur connected valence equalto x where x is a Whole number greater than two, said radicals being selected from the groups consisting of l designating a single carbon atom designating two adjacent carbon atoms and designating two carbon atoms joined to and separated by intervening structure.

This application is a division of my copending application Serial No. 240,067, filed August 2, 1952, now Patent No. 2,657,198.

What is claimed is:

1. Process of making a cyclic monomeric disulfide having the general formula S(CH2)1 m aZ(CH2)1 to a where Z is a member of the group consisting of O, S, OCH2O-, SCH2S, OC2H4O, SC2H4S, and -CH2, in which a product consisting essentially of an aqueous dispersion of a polymeric polyalkylene polysulfide having recurring units of the formula is subjected to steam distillation under alkaline conditions, the alkaline material being of the group consisting of alkali and alkaline earth hydroxides, obtaining a distillate and separating said monomeric disulfide from the distillate.

2. Process of making a cyclic monomeric disulfide having the general formula where Z is a member of the group consisting of O, S, -OCH2O-, SCH2S-, OC2H4O, SC2H4S-, and CH2, which comprises subjecting to dry distillation a mixture of a polysulfide polymer and about 5 to per cent by weight of a caustic alkali at pressures of about 0.1 mm. to 20.0 mm. and temperatures of about 50 C. to 500 C. until the distillation of the monomeric disulfide slows to an inappreciable rate, said polysulfide polymer comprising recurring units selected from the group consisting of SRS and R (S)a: where S is a sulfur atom, R is a radical having a sulfur-connected valence of two and R is a radical having a sulfur-connected valence equal to x where x is a whole number greater than two, said radicals being selected from the groups consisting of designating two carbon atoms joined to and separated by intervening structure, obtaining a distillate and separating said monomeric disulfide from the distillate.

References Cited in the file of this patent UNITED STATES PATENTS Ter Horst Jan. 12, 1937 Bonstein Dec. 14, 1937 OTHER REFERENCES Patrick, Trans. Faraday Soc. 32 (1936), pp. 347-58. 

1. PROCESS OF MAKING A CYCLIC MONOMERIC DISULFIDE HAVING THE GENERAL FORMULA 